Cardiac valves, so called heart valves, are found in a number of embodiments made both of wholly artificial materials, such as titanium, pyrolytic carbon or the like, or manufactured from natural tissue of porcine or bovine origin, said materials being treated in a chemical manner so as to obtain desirable properties. All hitherto known back valves for such intended function are associated with severe disadvantages, among which the following may be mentioned.
The designs not based on natural tissue are all made as more or less complicated constructions which result in risk of failure or unsatisfactory function in other ways. Known valves are, furthermore, designed so as to occupy, in an open position, a essential part of the flow cross-section, thus offering resistance to the flow of blood. Many of the known valves are furthermore designed in an asymmetric way with concomitant inconveniences. Furthermore, the prior art cardiac valves have a design where protruding parts disturb the flow of blood and also result in undesired epithelial growth. Finally, it can be mentioned that known valves often are associated with inertia in their opening or closing movement which substantially reduces their efficiency.
Examples of prior art designs are found in U.S. Pat. Nos. 4,820,299 and 5,078,739. These known cardiac valves are subject to the disadvantages indicated above.